Unit 1: Chemistry of Life
Biology · Unit 1 · Paper 3

Chemistry of Life unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 34 terms and is the same for everyone, so a teacher can assign “Unit 1, Paper 3” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 36 min 33 points0/17 attempted
1

Nucleotide structure

2

Buffer

3

Lipid structure

4

Carbohydrate structure and function

5

Denaturation

6

Nucleic acid directionality

7

Dehydration synthesis

8

Antiparallel strands

9

Peptide bond

10

Saturated vs unsaturated fat

11

Disulfide bridge

12

Directionality and complementarity

Short answer 1. Define or explain: Phospholipid amphipathicity

3 pts

Short answer 2. Define or explain: Carbonic acid–bicarbonate buffer

3 pts

Short answer 3. Define or explain: Surface tension

3 pts

Short answer 4. Define or explain: Monomers of the four macromolecules

3 pts

Free response

9 pts

This course has no free-response prompt tagged to this unit, so one from elsewhere in the course is used. It is still worth writing — the skill transfers.

A student performs a floating leaf disk assay. Spinach disks are vacuum-infiltrated so they sink, placed in 0.2% sodium bicarbonate solution, and illuminated by a lamp at four distances. The time for half the disks to float (ET50) is recorded: 10 cm, 8 min; 20 cm, 15 min; 30 cm, 30 min; 40 cm, 52 min. A fifth set of disks in bicarbonate-free water at 10 cm never floated.

Explain why the disks float and identify the gas responsible.

Describe the relationship between lamp distance and ET50 and explain it in terms of light intensity.

Explain the purpose of the bicarbonate-free set and state what its result demonstrates.

Predict and justify the result of repeating the 10 cm trial in the presence of DCMU, an inhibitor of electron transfer out of photosystem II.

Explain why moving the lamp introduces a confounding variable and describe how to control it.